This invention relates to intermediate compounds used to prepare herbicides. More particularly, it relates to intermediate compounds used to prepare herbicidal compounds disclosed in U.S. Pat. No. 4,393,506, and U.S. application Ser. No. 392,364, now adandoned.
The Journal of Organic Chemistry, 27, pages 1705-1706 (1962) and references cited therein disclose the reaction of saccharin with alcohols in the presence of hydrochloric acid or methanesulfonic acid to give 2-sulfamylbenzoic acid esters. However, no suggestion is set out for the separation of the desirable 2-sulfamylbenzoic acid ester from residual saccharin. One skilled in the organic chemical art might employ a caustic wash to remove the saccharin. However, upon treatment with caustic wash, o-carboxybenzene sulfonamide goes back to saccharin. In fact, during caustic treatment, a stable pH end point cannot be achieved. In addition, an O-ethylsaccharin by-product survives the caustic treatment, leaving the final intermediate product contaminated with several percent of this unwanted by-product.